A modern wind energy converter known in the art comprises a wind turbine placed on and rigidly connected to a wind turbine foundation. The wind turbine comprises a tower and a wind turbine nacelle positioned on top of the tower. A wind turbine rotor, comprising one or more wind turbine blades, is connected to the nacelle through a low speed shaft, which extends out of the nacelle front.
Controlling the temperature of electrical and mechanical components—particularly during operation of the components—has always been a problem and especially within the art of wind energy converters, this problem has been profound. Often the same wind energy converter type has to be able to operate in both extremely hot and extremely cold areas of the globe, which makes heavy demands on the wind energy converters system for controlling the temperature of especially wind turbine components such as gear, generator, power handling equipment, bearings and other.
Even though modern wind turbines often become more and more efficient in converting the rotation of the wind turbine rotor to power, the process will always result in some of the energy being converted to heat in some of the wind turbine components.
This excess heat must be removed from the components to protect the components and for them to function properly. Traditionally this has been done by means of one or more cooling systems, which by means of a cooling medium can transport the heat from the components to a radiator, which can give off the heat to the air outside the wind turbine and/or by creating an air flow of air from the outside of the wind turbine which passes the components.
But the quality of the outside air is difficult to control both in temperature, humidity, purity and other. Furthermore, modern wind turbines get bigger and bigger in power output and thereby often also in production of excess heat and this matched with the fact that air is a relatively poor conductor of heat, make these types of cooling systems very large, expensive and heavy.
Even further, the fact that the temperature of the air outside the wind turbine varies a lot from site to site, from day to night and from season to season—in extreme cases from −30° to +50° Celsius—in some cases will result in wind energy converters with an over-dimensioned and expensive cooling system. This problem could of course be overcome by adapting the temperature control system of the wind energy converter to the specific erection site, but this would be logistically difficult, expensive and prolong the time of delivery of the wind energy converters.
Another way of controlling the temperature of wind turbine components is disclosed in American patent No U.S. Pat. No. 6,676,122 B1, where the cooling system cools the components in the nacelle and the tower by circulating air inside the tower and the nacelle, making it give off heat through the surface of the tower and nacelle. But such a system is both complex and difficult to implement and since wind turbines usually produce the majority of the power during the day (because of more wind during the day), it usually also needs the most cooling during the day, where the sun and the ambient temperature will heat up the surface of the wind turbine. Such a system will therefore have to have a very large cooling capacity to be able to work properly, making the system itself very large and expensive.
Regarding offshore wind energy converters it is known to use seawater to cool different components of the wind turbine, but if the cooling system is open there are serious problems regarding ice, clogging, corrosion and other, which are difficult and expensive to solved, and if the system is closed e.g. by circulating the cooling medium through a hose placed in the seawater there is ice, storm, overgrowing and other to be solved. The problems of both these systems being complicated and expensive to overcome and no matter how it is done, this technique is only feasible in relation to offshore wind energy converters.
Another way of controlling the temperature in a wind turbine is disclosed in DE 10 2004 061 391 A1 where air is being drawn through cable canals in the wind turbine foundation to lower the temperature of the air before it is used to cool equipment in the tower of a wind turbine. But this cooling system is not very efficient and is contains several of the previously mentioned drawbacks such as difficulties in controlling the quality and other.
It is therefore an object of the invention to provide for a wind energy converter without the above mentioned disadvantages.
Especially it is an object of the invention to provide for an advantageous and cost-efficient technique for controlling the temperature of one or more areas of a wind energy converter, particularly regarding where and how to give off excess heat and/or absorb needed heat.